Photocatalytic reduction of nitrate ions over tantalate photocatalysts

Tantalate photocatalysts reduced nitrate ions to nitrite ions, dinitrogen, and ammonia under UV irradiation even without co-catalysts or reducing reagents such as organic compounds. The photocatalytic activities of tantalate photocatalysts were larger than those of TiO2 photocatalysts. The selectivity for the photocatalytic reduction of nitrate ions was affected by the addition of co-catalysts. In particular, the efficiencies of dinitrogen and ammonia formation increased by one to two orders of magnitude when a Ni co-catalyst was loaded. The selectivity was also affected by the amount of loaded Ni and the loading method. 44% and 39% of nitrate ions in an aqueous KNO3 solution (0.010 mol L−1, 400 mL) were reduced to dinitrogen and ammonia, respectively, over the Ni(1 wt.%)/KTaO3 photocatalyst after 25 h irradiation.